Variable elliptical and variable profile turning attachment for a lathe

ABSTRACT

An attachment used on a lathe to turn pistons includes a tool which is driven through two reciprocal strokes for each revolution of the lathe spindle to provide an elliptical crosssectional configuration on the piston includes means for varying the stroke of the tool in accordance with a predetermined pattern so that the elliptical cross-sectional configuration is varied, and also includes means to vary the position of the tool independently of the stroke of the tool in accordance with a predetermined pattern so that the profile of the piston is varied.

ilnited StatesPatent 1191 Johnston et al.

[4 1 Apr. 16, 1974 VARIABLE ELLIPTICAL AND VARIABLE PROFILE TURNING ATTACHMENT FOR A LATHE 1 Inventors: Dale Montieth Johnston; Nelson Paul Keith, both of Waterloo, Iowa Assignee: Deere & Company, Moline, 111.

Filed: May 25, 1972 Appl. No.: 257,019

US. Cl. 82/19 Int. Cl. B23b 3/28 Field of Search 82/18, l9, 14

References Cited UNITED STATES PATENTS 10/1968 Fevveirinha 82/18 10/1955 Chang 8 2/19 8/1964 Cafolla...; 82/14 2,782,668 2/1957 Richet 82/14 1,350,735 8/1920 Phillips 82/18 X 1,935,007 11/1933 Bickel.... 82/18 2,008,474 7/1935 Smith 82/18 Primary ExaminerHarrison L. I-linson [5 7] ABSTRACT An attachment used on a lathe to turn pistons includes a tool which is driven through two reciprocal strokes for each revolution of the lathe spindle to provide an elliptical cross-sectional configuration on the piston includes means for varying the stroke of vthe tool in accordance with a predetermined pattern so that the elliptical cross-sectional configuration is varied, and also includes means to vary the position of the tool independently of the stroke of the tool in accordance with a predetermined pattern so that the profileof the piston is varied.

20 Claims, 8 Drawing Figures PATENVEDAPR 16 1914 3.803357 SHEET 1 OF 3 PATENTEMPR is I974 SHEET 3 [IF 3 VARIABLE ELLIPTICAL AND VARIABLE PROFILE TURNING ATTACHMENT FOR A LATHE BACKGROUND OF THE INVENTION The present invention relates generally to a piston turning attachment for use with a lathe, and more particularly relates to such an attachment which will provide a piston with a varying elliptical cross-sectional configuration and will also provide the piston with a varying profile.

Because of the numerous materials used for the various components of the modern internal combustion engine, it is necessary to make provision for the varying coefficients of thermal expansion of the materials. For example, many engines include aluminum pistons within a cast iron block. Because aluminum has a greater coefficient of thermal expansion thandoes the cast iron, it is necessary tomake the piston slightly 'undersized so that it will not freeze within the cylinder when the engine warms up. This is generally accomplished by providing the piston with an elliptical crosssectional configuration so that there are two opposed surfaces which act as bearing surfaces to engage the cylinder before the engine warms ups. Also, it is often desirable to provide the piston with a varying elliptical cross-sectional configuration. For example, it may be desirable to have different elliptical cross-sectional configurations at the extreme ends of the piston skirt.

SUMMARY OF THE INVENTION,

The principal object of the present invention is to provide a simple piston turning attachment for use with a lathe which will provide the piston with a varying elliptical cross-sectional configuration.

Another object of the present invention is to provide a piston turning attachment for use with a lathe which will simultaneously provide the piston with a varying elliptical cross-sectional configuration and a varying profile.

Still another object of the present invention is provide a piston turning attachment for use with a lathe which provides pistons with varying elliptical crosssectional configurations and varying profile, which includes provision for simple replacement of guide bars.

to vary the elliptical cross-sectional configuration and the profile. v g

The above objects and additional objects and advantages of the present invention will become obvious to those skilled in the art from a reading of the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

' FIG. 1 is a side elevational view of a lathe on which the turning attachment according to the present invention has been mounted;

FIG. 2 is a top plan view of the lathe and turning attachment illustrated in FIG. 1;

FIG. 3 is a cross-sectional view taken substantially along the line 33 of FIG. 2;

FIG. 4 is an elevational view of the right-hand end of the lathe and turning attachment illustrated in FIG. 1;

FIG. 5 is an enlarged view of a portion of the turning DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the piston turning attachment according to the present invention is illustrated as being mounted on a lathe which includes a bed 10, a headstock 12, a tailstock 14 and a carriage 16. A hollow spindle 18 extends through and is joumaled in the headstock 12 and has a chuck 20 fixed to one end thereof. A motor 22 is mounted on the bed and serves to drive the spondle 18 through a chain or belt 24 and suitable gears .or pulleys on the output shaft of the motor 22 and the spindle l8.

A threaded rod 26 is supported along one side of the bed and extends through an apron 28 of the carriage 16. As is conventional, the apron 28 includes internal gearing in engagement with the threaded rod 26 and controlled by a crank 30 so that upon rotation of the crank 30, the carriage is moved along the bed.

A cross'slide 32 is mounted on the carriage 16 for movement perpendicular to the lathe bed. A dovetail connection 34 between the carriage and cross slide limits the movement of the cross slide on the carriage to V a direction perpendicular to the lathe bed.

The lathe as thus far described is of conventional I 42. The shaft 40 is connected to one section 44 of a telescopic drive shaft through a universal joint 46. The

other section 48 of the telescopic drive shaft is connected through a universal joint 50 to a shaft 52 which is joumaled in a bearing block 54 secured to the headstock 12. The shaft 52 is driven from the spindle 18 by a chain or belt 56 and gears or pulleys mounted on the shaft 52. and spindle 18. The gears or pulleys on the shaft 52 and spindle 18 are of equal size so that the shaft 40 is driven at the same angular velocity as the spindle 18.

A hub 58 having a central aperture of a diameter greater than the diameter of the shaft 40 is mounted on the shaft 40 within the support 36. The hub 58 is provided with opposed radially extending bores 60, and bearings 62 are pressed into the bores 60. A pin 64 extends through an apertue provided in the shaft 40 and through the bearings 62 to constrain the hub 58 for rotation with the shaft 40 and to permit tilting of the hub 58 with respect to the shaft 40 about the pin 64. The pin 64 has a pressed fit in the aperture provided on the shaft 40 to retain the hub 58 in the proper position with respect to the shaft 40. A ring 66 of hardened material is pressed over the hub 58 and forms a circular cam which, due to the mounting of the hub 58 on the shaft 40, can be tilted with respect to the shaft 40.

A tool support 68 is mounted on the support 36 in any suitable manner. A turning toll 70 is reciprocally mounted in the support 68 and has a working end projecting therefrom. Within the support 68, the bottom of the tool 70 is notched to receive a roller 72 carried by an actuating arm 74. The actuating arm 74 has one end pivotally mounted on the tool support 68 by a pin 76 and its opposite end is biased toward the cam 66 by a light spring 78. A cam follower 80 is mounted for reciprocal movement in the support 68 and has opposite ends engaging the cam 66 and actuating arm 74. When the cam 66 is in the position illustrated in FIGS. and 6, the tool 70 will be stationary since the circular cam 66 is normal to the shaft 40. However, when the cam 66 is tilted with respect to the shaft 40, as will be explained hereinafter, to tool 70 will be driven through two reciprocal cycles for each full revolution of the shaft 40.

A sleeve 82 is slidably mounted on the shaft 40, within the support 36 and has a pair of axially spaced flanges 84 and 86 secured to one end thereof. A compression spring 88 which encircles the sleeve 82 has one end in engagement with the flange 84 and its other end in engagement with a collar 90 slidably mounted on a sleeve 82. The collar 90 engages the outer ends of a pair of opposed ears 92 which are secured to the hub 58 and extend axially therefrom alongside the sleeve 82. Each of the ears 92 is provided with an obliquely extending slot 94, and a pair of opposed radially extending pins 96 carried by the sleeve 82 extend through the slots 94. Bearings 98 on the ends of the pins 96 are positioned in the slots 94 to keep the resistance between the pins 96 and slots 94 at a minimum.

The spring 88 acting on the collar 90 and flange 84 urges the sleeve 82 away from the hub 58, and this moves the bearing 98 to the outer ends of the slots 94. The slots 94 are positioned such that when the bearings 98 are in the outer end of the slots 94, the cam 66 is normal to the shaft 44. If the sleeve 82 is moved toward the cam 66 against the bias of the spring 88, the pins 96 and bearings 98 pivot the hub 58 and cam 66 about the pins 64 so that the cam 66 is tilted with respect to the shaft 40. When the cam 66 is tilted with respect to the shaft 40, its outline in a plane normal to the shaft 44 and through the centerline of the follower 80'is elliptical, and the elliptical outline varies as the degree of tilt is varied.

A cross shaft 100 is journaled between the side walls on the support 36 and has a pair of arms 102 secured thereto and extending upwardly therefrom alongside the flanges 84 and 86. A roller 104 is journaled on the outer end of each of the arms 102 between the flanges 84 and 86 by a pin 106 so that movement of the shaft about its axis shifts the sleeve 82 on the shaft 40. The supports 36 and 68, along with the parts supported therein, will at times hereinafter be referred to collectively as an elliptical generator.

The cross shaft 100 is moved about its axis by a control arm 108 which has one end secured to the shaft 100 and has a roller or follower 110 mounted on its opposite end. The roller 110 moves along the guide face of an elliptical generator guide bar 112 which is mounted on the tailstock 14. The guide bar 112 is provided with a pair of spaced elongated slots 114, and a pair of bolts 116 extend through the slots and into threaded bores provided in the tailstock 14 to retain the guide bar 112 on the tailstock. A small block 118 secured to each end of the tailstock 14 has a threaded vertically extending aperture which contains a set screw 120. The set screws 120 engage a pair of stop blocks 122 provided on the backside of the guide bar 1 12 as an aid to the proper positioning of the guide bar 112. Once the set screws 120 have been set for the proper positioning of the guide bar, one guide bar can be easily removed and replaced with another whenever it is desired to change the cross-sectional configuration of the pistons to be machined.

A profile guide bar support table 124 is secured to the side of the bed 10 by brackets 126, and a profile guide bar 128 is removably mounted on the table. One end of the profile guide bar is pivotally mounted on the table 124 by a bolt 130 while the opposite end of the guide bar is provided with an elongated slot which receives a bolt 132. The slot 132 permits proper positioning of the profile guide bar 128 on the table 124.

The cross slide 32 is moved on the carriage 16 in accordance with the contour of a guide face 136 of the profile guide bar 128 by a roller or follower 138. The roller 138 is mounted on the lower end ofa vertical arm 140 which depends from a horizontally extending rigid arm 142 secured to the cross slide 32 by fastener means in the form of one or more bolts 144. The arm 140 is rigidly secured to the arm 142 midway along the length thereof, and an additional generally vertically extending arm 146 is pivotally connected to the outer end of the arm 142 by a hinge 148. The arm 146 carries a roller 150 at its lower end which engages the face of the profile guide bar 128 opposite from the guide face 136. The arm 146 is biased toward the arm 140 by a spring 152.

In order to mount a piston to be turned on the lathe, a cup 154 is held by the chuck 20 and a skirt ofa piston 156 is positioned over the cup 154. A threaded rod 158 extends through the spindle 18 and is turned into a threaded aperture provided in an undersized wrist pin 160 in the piston 156. A hand wheel 162 on the outer end of the rod 158 is used to thread the rod 158 into the wrist pin to securely clamp the piston 156 on the cup 154.

To operate the lathe and turning attachment according to the present invention, the piston 156 is mounted on the spindle 18 in the manner set forth above, and the proper elliptical generator and profile guide bars 112 and 128 are mounted on the tailstock and profile, guide bar support table. The motor 122 is then turned on to drive the spindle l8 and shaft 40. The operator will then turn the wheel or crank 30 to move the carriage 16 along the bed 10. As the carriage 16 moves along the bed, the roller 110 will follow the contour of the guide face of the elliptical'generator guide bar 1 l2 and move the control arm 108 about the axis of the shaft 100 in accordance with the contour of the guide face of the elliptical generator guide bar. As the control arm 108 moves about the axis of the shaft 100, it moves the shaft 100 about itsaxis which, through the arms 102, moves the sleeve 82 along the shaft 40 to change the degree of tilt of the cam 66 which in turn changes the length of the reciprocal stroke of the cam follower 80 and the tool 70.

Also, as the carriage 16 moves along the bed 10, the follower 138 moves along the-guide face of the profile guide bar 128 to move the cross slide 32 on the carriage 16 in accordance with the contour of the guide face of the profile guide bar 128. As the cross slide 32 moves on the carriage 16, the tool 70 is moved toward and/or away from the piston 156 independently of its reciprocal movement in the support 68 so that the profile of the turned piston will vary in accordance with the profile of the guide face 136 of the profile guide bar 128.

The finished piston will have a varying profile and a varying elliptical cross-sectional configuration generally as shown in FIGS. 7 and 8 where the profile and elliptical cross-sectional configuration of the piston are greatly exaggerated for illustration purposes. As can be seen from FIG. 7, the profile of the skirt portion of the cylinder varies irregularly from the top to the bottom thereof, and as can be seen from FIG. 8, the elliptical cross-sectional configuration of the top of the piston is different from that of the bottom of the piston. Due to the straight line guide face of the elliptical generator guide bar 1 12, there is a uniform transition in the elliptical cross-sectional configuration of the piston from the top to the bottom.

From the foregoing description of construction and operation, it can be seen that the present invention provides a simple attachment for a lathe which is particularly useful for turning pistons and which will provide a varying elliptical cross-sectional configuration and a varying profile on the piston.

Having described one preferred embodiment of the invention, various modifications within the spirit and scope of the invention will become apparent to those skilled in the art and can be made without departing from the underlying principles of the invention. Therefore, the invention should not be limited to the specific illustration and description, but only by the following claims.

We claim:

1. A variable elliptical turning attachment for use on a lathe including a bed, a headstock having a driven spindle, and a carriage movable along the-bed, the attachment comprising: a support member mountable on the carriage for movement therewith; a shaft journaled on the support member in parallel relation to the spindle; means for driving the shaft at an angular velocity equal to the angular velocity of the spindle; a circular cam mounted on the shaft for rotationtherewith and for tilting movement about an axis perpendicular to the axis of the shaft; a cam follower in engagement with the circular cam carrier by the support member for reciprocal movement perpendicular to the axis of the shaft; a tool associated with the follower for reciprocal movement therewith; a cam bar mountable on the bed and including a cam control surface; a control lever having one end pivotally mounted on the support member and having a follower at its other end for engagement with the cam control surface of the cam bar, whereby as the carriage moves along the bed the lever will pivot according to the contour of the cam control surface; and means carried by the, support member acting between the lever and circular cam to tilt the circular cam in ac 7 port member, arm means secured to the shaft and engageable with abutment means on the sleeve to move the sleeve longitudinally of the first-mentioned shaft upon angular movement of the cross-shaft, and wherein the one end of the lever is secured to the cross shaft.

3. A variable elliptical turning attachment as set forth in claim 2 wherein spring means normally bias the circular cam to a position normal to the first-mentioned shaft.

4. A variable elliptical turning attachment as set forth in claim 2 wherein the pin is seated in one extreme end of the slot when the circular cam is normal to the firstmentioned shaft, and spring means normally'urges the sleeve in a direction to move the pin to the one extreme end of the slot.

5. A variable elliptical turning attachment as set for in claim 4 wherein the spring means includes a compression spring encircling the sleeve and acting between the abutment means on the sleeve and the ear.

6. A variable elliptical turning attachment as set forth in claim 2 wherein reducing means acts between the cam follower and tool to reduce the reciprocal movement of the tool to a fi'xed percentage of the reciprocal movement of the cam follower.

7. Variable elliptical, variable profile turning apparatus for attachment to and use with a lathe having a bed, a headstock including a driven spindle; a carriage movable along the bed and including a cross slide movable on the carriage in a direction perpendicular to the movement of the carriage, the apparatus comprising: a profile generator securable to the bed and including a removable and replaceable profile guide bar having a profile guide face; means securableto the cross slide and associated with the profile guide bar to move the cross slide in accordance with the profile of the guide face as the carriage moves along the bed; a support member mountable on the cross slide for movement therewith; a shaft journaled on the support member parallel to the spindle; means for driving the shaft at an angular velocity equal to the angular velocity of the spindle;.a circular cam mounted on the shaft for rotation therewith and for tilting movementabout an axis perpendicular to the axis of the shaft; tool means including a cam follower in engagement with the circular cam carried by the support for reciprocal movement relative thereto; an elliptical generator guide bar mountable on the bed and including an elongated con trol surface; a control lever having one end pivotally mounted on the support member and having a follower on its other end for engagement with the control surface whereby the lever will move about its pivotal connection with the support member in accordance with the contour of the control surface as the carriage moves along the bed; and means carried by the support member and acting between the circular cam and lever to tilt the circular cam in accordance with the pivotal movements of the lever.

8. Variable elliptical, variable profile turning apparatus as set forth in claim 7 wherein the means associated -with the profile guide bar includes first and second follower members engageable with opposed faces of the guide bar, the first follower member is fixed with respect to the cross slide and engages the guide face, and the second follower member is movable with respect to the first follower member and is yieldably biased toward the first follower member.

9. Variable elliptical, variable profile turning apparatus as set forth in claim 8 wherein the elliptical generator guide bar is mountable on a tailstock which is slidably mounted on the bed whereby the elliptical generator guide bar can be moved with respect to the support member for proper positioning of the elliptical generator guide bar.

10. Variable elliptical, variable profile turning apparatus as set forth in claim 8 wherein the means acting between the lever and circular cam includes a sleeve slidably mounted on the shaft, an ear secured to the circular cam and extending alongside the sleeve, an elongated oblique slot provided in the car, a pin extending perpendicular to the shaft carried by the sleeve and extending through the slot; a cross shaft rotatably supported on the support member, arm means secured to the shaft and engageable with abutment means on the sleeve to move the sleeve longitudinallyof the firstmentioned shaft upon angular movement of the cross shaft, and wherein the one end of the lever is secured to the cross shaft.

11. Variable elliptical, variable profile turning apparatus as set forth in claim 10 wherein spring means normally bias the circular cam to a position normal to the first-mentioned shaft.

12. Variable elliptical, variable profile turning apparatus as set forth in claim 11 wherein the pin is seated in one extreme end of the slot when the circular cam is normal to the first-mentioned shaft, and spring means normally urges the sleeve in a direction to move the pin to the one extreme end of the slot.

13. Variable elliptical, variable profile turning apparatus as set forth in claim 12 wherein'the spring means includes a compression spring encircling the sleeve and acting between the abutment means on the sleeve and the car.

14. Variable elliptical, variable profile turning apparatus as set forth in claim 13 wherein the elliptical generator guide bar is mountable on a tailstock slidably mounted on the bed, the tailstock is provided with a pair of bolt-receiving threaded bores, and the elliptical generator guide bar is provided with a pair of vertically elongated slots mating with the apertures whereby, when the elliptical generator guide bar is mounted on the tailstock by a pair of bolts extending through the slots and into the threaded apertures, the elliptical generator guide bar can be adjusted horizontally by movement of the tailstock and vertically due to the elongated slots.

15. Apparatus for machining pistons to provide a varying elliptical cross-sectional configuration and a varying profile comprising: an elongated lathe bed; a headstock mounted on one end of the bed and including a driven spindle; means for mounting a piston on the spindle coaxial therewith and for rotation therewith; a carriage slidably mounted on the bed for movement parallel to the axis of the spindle and including a cross slide movable perpendicular to the movement of the carriage; a profile attachment secured to the bed and including a profile guide bar extending generally parallel to the axis of the spindle and having a guide face; first follower means secured.to the cross slide and engaging the guide face of the profile guide bar to move the cross slide in accordance with the contour of the guide face as the carriage is moved along the bed; an elliptical generator mounted on the cross slide and including a tool engageable with the piston and reciprocal perpendicular to the axis of the spindle, a shaft journaled on the elliptical generator, means for driving the shaft at an angular velocity equal to the angular velocity of the spindle, and means mounted on and driven by the shaft operatively associated with the tool for driving the tool through two complete reciprocal cycles for each complete revolution of the shaft; an elliptical generator guide bar mounted on the bed and including an elongated guide face extending generally parallel to the axis of the spindle; and second follower means in engagement with the guide face of the elliptical generator guide bar and associated with the elliptical generator to vary the length of the tool stroke in accordance with guide bar as the carriage moves along the bed.

16. Apparatus as set forth in claim 15 wherein the means mounted on and driven by the shaft includes a circular cam mounted concentrically on the shaft for rotation therewith and being tilted with respect to the axis of the shaft; and a cam follower in engagement with the circular cam and in driving association with the tool.

17. Apparatus as set forth in claim 16 wherein the elliptical generator includes means to vary the tilt of the circular cam with respect to the axis of the shaft, and the second follower means acts on the last mentioned means to vary the tilt of the circular cam in accordance with the contour of the guide face of the elliptical generator guide bar.

18. Apparatus as set forth in claim 17 wherein the circular cam is mounted for pivotal movement about an axis perpendicular to the axis of the shaft and the means to vary the tilt of the circular cam includes a sleeve slidably mounted on the shaft, an ear secured to the side of the circular cam and extending alongside the sleeve, an elongated oblique slot provided in the ear; a pin extending carried by the sleeve and extending through the slot, and means for acting on the sleeve and interconnected with the second follower means to move the sleeve along the shaft in accordance with the I the contour of the guide face of the elliptical generator 20. Apparatus as set forth in claim 19 wherein the engages the guide face of the profile guide bar, and the first follower means includes first and second followers second follower is movable with respect to the first folengaging opposite faces of the profile guide bar, the lower and is yieldably biased toward the first follower. first follower is fixed with respect to the cross slide and 

1. A variable elliptical turning attachment for use on a lathe including a bed, a headstock having a driven spindle, and a carriage movable along the bed, the attachment comprising: a support member mountable on the carriage for movement therewith; a shaft journaled on the support member in parallel relation to the spindle; means for driving the shaft at an angular velocity equal to the angular velocity of the spindle; a circular cam mounted on the shaft for rotation therewith and for tilting movement about an axis perpendicular to the axis of the shaft; a cam follower in engagement with the circular cam carrier by the support member for reciprocal movement perpendicular to the axis of the shaft; a tool associated with the follower for reciprocal movement therewith; a cam bar mountable on the bed and including a cam control surface; a control lever having one end pivotally mounted on the support member and having a follower at its other end for engagement with the cam control surface of the cam bar, whereby as the carriage moves along the bed the lever will pivot according to the contour of the cam control surface; and means carried by the support member acting between the lever and circular cam to tilt the circular cam in accordance with the pivotal movement of the lever.
 2. A variable elliptical turning attachment as set forth in claim 1 wherein the means acting between the lever and circular cam includes a sleeve slidably mounted on the shaft, an ear secured to the circular cam and extending alongside the sleeve, an elongated oblique slot provided in the ear, a pin extending perpendicular to the shaft carried by the sleeve and extending through the slot; a cross shaft rotatably supported on the support member, arm means secured to the shaft and engageable with abutment means on the sleeve to move the sleeve longitudinally of the first-mentioned shaft upon angular movement of the cross-shaft, and wherein the one end of the lever is secured to the cross shaft.
 3. A variable elliptical turning attachment as set forth in claim 2 wherein spring means normally bias the circular cam to a position normal to the first-mentioned shaft.
 4. A variable elliptical turning attachment as set forth in claim 2 wherein the pin is seated in one extreme end of the slot when the circular cam is normal to the first-mentioned shaft, and spring means normally urges the sleeve in a direction to move the pin to the one extreme end of the slot.
 5. A variable elliptical turning attachment as set forth in claim 4 wherein the spring means includes a compression spring encircling the sleeve and acting between the abutment means on the sleeve and the ear.
 6. A variable elliptical turning attachment as set forth in claim 2 wherein reducing means acts between the cam follower and tool to reduce the reciprocal movement of the tool to a fixed percentage of the reciprocal movement of the cam follower.
 7. Variable elliptical, variable profile turning apparatus for attachment to and use with a lathe having a bed, a headstock including a driven spindle; a carriage movable along the bed and including a cross slide movable on the carriage in a direction perpendicular to the movement of the carriage, the apparatus comprising: a profile generator secuRable to the bed and including a removable and replaceable profile guide bar having a profile guide face; means securable to the cross slide and associated with the profile guide bar to move the cross slide in accordance with the profile of the guide face as the carriage moves along the bed; a support member mountable on the cross slide for movement therewith; a shaft journaled on the support member parallel to the spindle; means for driving the shaft at an angular velocity equal to the angular velocity of the spindle; a circular cam mounted on the shaft for rotation therewith and for tilting movement about an axis perpendicular to the axis of the shaft; tool means including a cam follower in engagement with the circular cam carried by the support for reciprocal movement relative thereto; an elliptical generator guide bar mountable on the bed and including an elongated control surface; a control lever having one end pivotally mounted on the support member and having a follower on its other end for engagement with the control surface whereby the lever will move about its pivotal connection with the support member in accordance with the contour of the control surface as the carriage moves along the bed; and means carried by the support member and acting between the circular cam and lever to tilt the circular cam in accordance with the pivotal movements of the lever.
 8. Variable elliptical, variable profile turning apparatus as set forth in claim 7 wherein the means associated with the profile guide bar includes first and second follower members engageable with opposed faces of the guide bar, the first follower member is fixed with respect to the cross slide and engages the guide face, and the second follower member is movable with respect to the first follower member and is yieldably biased toward the first follower member.
 9. Variable elliptical, variable profile turning apparatus as set forth in claim 8 wherein the elliptical generator guide bar is mountable on a tailstock which is slidably mounted on the bed whereby the elliptical generator guide bar can be moved with respect to the support member for proper positioning of the elliptical generator guide bar.
 10. Variable elliptical, variable profile turning apparatus as set forth in claim 8 wherein the means acting between the lever and circular cam includes a sleeve slidably mounted on the shaft, an ear secured to the circular cam and extending alongside the sleeve, an elongated oblique slot provided in the ear, a pin extending perpendicular to the shaft carried by the sleeve and extending through the slot; a cross shaft rotatably supported on the support member, arm means secured to the shaft and engageable with abutment means on the sleeve to move the sleeve longitudinally of the first-mentioned shaft upon angular movement of the cross shaft, and wherein the one end of the lever is secured to the cross shaft.
 11. Variable elliptical, variable profile turning apparatus as set forth in claim 10 wherein spring means normally bias the circular cam to a position normal to the first-mentioned shaft.
 12. Variable elliptical, variable profile turning apparatus as set forth in claim 11 wherein the pin is seated in one extreme end of the slot when the circular cam is normal to the first-mentioned shaft, and spring means normally urges the sleeve in a direction to move the pin to the one extreme end of the slot.
 13. Variable elliptical, variable profile turning apparatus as set forth in claim 12 wherein the spring means includes a compression spring encircling the sleeve and acting between the abutment means on the sleeve and the ear.
 14. Variable elliptical, variable profile turning apparatus as set forth in claim 13 wherein the elliptical generator guide bar is mountable on a tailstock slidably mounted on the bed, the tailstock is provided with a pair of bolt-receiving threaded bores, and the elliptical generator guide bar is provided with a pair of vertically elongated slots mating with the apertures whereby, when The elliptical generator guide bar is mounted on the tailstock by a pair of bolts extending through the slots and into the threaded apertures, the elliptical generator guide bar can be adjusted horizontally by movement of the tailstock and vertically due to the elongated slots.
 15. Apparatus for machining pistons to provide a varying elliptical cross-sectional configuration and a varying profile comprising: an elongated lathe bed; a headstock mounted on one end of the bed and including a driven spindle; means for mounting a piston on the spindle coaxial therewith and for rotation therewith; a carriage slidably mounted on the bed for movement parallel to the axis of the spindle and including a cross slide movable perpendicular to the movement of the carriage; a profile attachment secured to the bed and including a profile guide bar extending generally parallel to the axis of the spindle and having a guide face; first follower means secured to the cross slide and engaging the guide face of the profile guide bar to move the cross slide in accordance with the contour of the guide face as the carriage is moved along the bed; an elliptical generator mounted on the cross slide and including a tool engageable with the piston and reciprocal perpendicular to the axis of the spindle, a shaft journaled on the elliptical generator, means for driving the shaft at an angular velocity equal to the angular velocity of the spindle, and means mounted on and driven by the shaft operatively associated with the tool for driving the tool through two complete reciprocal cycles for each complete revolution of the shaft; an elliptical generator guide bar mounted on the bed and including an elongated guide face extending generally parallel to the axis of the spindle; and second follower means in engagement with the guide face of the elliptical generator guide bar and associated with the elliptical generator to vary the length of the tool stroke in accordance with the contour of the guide face of the elliptical generator guide bar as the carriage moves along the bed.
 16. Apparatus as set forth in claim 15 wherein the means mounted on and driven by the shaft includes a circular cam mounted concentrically on the shaft for rotation therewith and being tilted with respect to the axis of the shaft; and a cam follower in engagement with the circular cam and in driving association with the tool.
 17. Apparatus as set forth in claim 16 wherein the elliptical generator includes means to vary the tilt of the circular cam with respect to the axis of the shaft, and the second follower means acts on the last mentioned means to vary the tilt of the circular cam in accordance with the contour of the guide face of the elliptical generator guide bar.
 18. Apparatus as set forth in claim 17 wherein the circular cam is mounted for pivotal movement about an axis perpendicular to the axis of the shaft and the means to vary the tilt of the circular cam includes a sleeve slidably mounted on the shaft, an ear secured to the side of the circular cam and extending alongside the sleeve, an elongated oblique slot provided in the ear; a pin extending carried by the sleeve and extending through the slot, and means for acting on the sleeve and interconnected with the second follower means to move the sleeve along the shaft in accordance with the movement of the second follower means.
 19. Apparatus as set forth in claim 18 wherein abutment means are provided on the sleeve, and the means acting on the sleeve and interconnected with the second follower means includes a cross shaft journaled on the elliptical generator, arm means on the shaft engaging the abutment means to move the sleeve in accordance with the movement of the cross shaft, and a lever having one end secured to the cross shaft; and the second follower means is mounted on the second end of the lever.
 20. Apparatus as set forth in claim 19 wherein the first follower means includes first and second followers engaging opposite faces of the profile guide bar, the firSt follower is fixed with respect to the cross slide and engages the guide face of the profile guide bar, and the second follower is movable with respect to the first follower and is yieldably biased toward the first follower. 